U.S. Pat. Nos. 3,806,312; 3,934,970; 3,947,242; and 3,994,711 disclose glass tempering systems of the horizontal roller conveyor type for conveying glass sheets in a horizontal direction during a tempering process. Rolls in both the furnace and quench unit of each of the tempering systems disclosed by these patents are supported at their opposite ends and frictionally driven by continuous drive loops. Glass sheets supported on the upper sides of the rolls are conveyed therealong first through the furnace where heating takes place and then through the quench unit where quench gas supplied by upper and lower blastheads provides rapid cooling of the heated glass to perform the tempering.
One conventional type of quench roll for horizontal roller conveyor type systems for tempering glass sheets includes a central steel shaft and a flexible metallic component embodied by all metal wire or a helical spring wrapped about the shaft in a helical configuration so as to reduce the area of contact between the roll and the lower surface of a glass sheet supported on the roll. Such helical metallic components increase the lower glass sheet surface area subjected to quenching gas and thereby increase the degree to which the tempering is performed. In addition, the helical metallic components prevent lifting of conveyed glass sheets by facilitating the escape of spent quenching gas downwardly after impinging with the lower glass surface. Since the metallic components remain rigid at the temperature involved, the softened glass sheet can be marked by the more rigid helical metallic component if all of the furnace, quench unit, and conveying parameters are not properly selected.
Other types of quench rolls for horizontal roller conveyor type systems for tempering glass sheets include annular silicone rubber members received by a central steel shaft and asbestos rope wrapped helically around a central shaft. The major problem with these types of quench rolls is that the occassional glass sheet that breaks upon quenching cuts the annular silicone rubber member or the asbestos rope and the roll must then be repaired before further use.
Quench rolls for tempering relatively wide glass sheets have also included a central shaft along which glass fiber conveying discs are positioned to carry the glass during tempering. Such a quench roll construction increases the escape area for spent quenching gas supplied by a lower blasthead.